The decrement of food palatability associated with adoption of a reduced fat diet is a significant obstacle to attainment of the widely endorsed goal of moderating fat intake in the population. This proposed project will explore the relationship between fat intake and hedonic responses to foods with the aim of developing a strategy to ameliorate the loss of food acceptability and thereby improve adherence to a reduced fat diet. Work with salt and our preliminary studies with fat indicate that the sensory exposure to a food constituent, rather than its level of intake, is a primary determinant of the preferred level of the constituent in foods. To document this effect with fat, hedonic and intensity judgements of foods will be monitored in 128 healthy adults (50% female; at least 15% minority) randomly assigned to one of four diets: a) high fat intake-high sensory exposure, b) high intake-low exposure, c) low intake-high exposure and d) low intake-low exposure. To explore the amount of time these dietary manipulations must be enforced to elicit a maximal hedonic shift and to establish one that is persistent, responses of subjects on diets enforced for 3 or 6 months will be monitored. All subjects will be retested 6 months after diet termination. Hedonic responses will be obtained on an array of measures that address various aspects of hedonics (e.g., preferred concentration of fat in foods, preferred frequency of intake of various foods, overall responses to items with varying fat levels). Dietary compliance will be determined by diet records, urinary excretion values, levels of plasma constituents, changes in body weight and composition and the use of labeled foods. The effect of food familiarity and a potential influence of fat metabolism on sensory responsiveness will be explored as two possible mechanisms underlying a diet-induced hedonic shift. It is hypothesized that a hedonic shift for fats in foods can be established and exploited to promote long-term adherence to a reduced fat diet.